Description

The CHS-GM20-20BY is a compact 20mm diameter geared stepper motor designed for precise low-speed motion and positioning applications.

It combines a 2-phase, 4-wire bipolar stepper motor with an all-metal gearbox, providing multiple gear ratio options from 12.5:1 to 488:1. The motor can operate from 5V to 12V and is suitable for compact robotic mechanisms, automation equipment, miniature actuators, instruments, and positioning systems.

The 4mm D-shaped output shaft provides reliable mechanical coupling, while the wide selection of reduction ratios allows users to balance output speed, step resolution, and torque for different applications.

Key Features

Compact 20mm diameter geared stepper motor
2-phase, 4-wire bipolar configuration
All-metal reduction gearbox
5V–12V operating voltage range
Multiple gear ratios from 12.5:1 to 488:1
4mm D-shaped output shaft
10.5mm output shaft length
Fine positioning through gearbox reduction
Suitable for bidirectional CW/CCW operation
Compact design for robotics and automation

Specifications

Specification	Value
Model	CHS-GM20-20BY
Motor Type	Geared Stepper Motor
Motor Diameter	20 mm
Phase	2 Phase
Wiring	4 Wire
Drive Mode	Bipolar
Operating Voltage	5–12V DC
Rated Voltage for Reference Data	12V DC
Current per Phase	600 mA
Coil Resistance	20Ω ±7% / Phase
Coil Inductance	11 mH / Phase
Motor Step Angle	18°
Excitation Method	2-Phase Excitation
Output Shaft Diameter	4 mm
D-Shaft Flat Diameter	3.5 mm
Output Shaft Length	10.5 mm
D-Flat Length	7 mm
Recommended Pulse Frequency	300–1000 PPS
Maximum Response Frequency	>1200 PPS
Maximum Starting Frequency	>900 PPS
Holding Torque	>60 gf·cm at 0 PPS
Pull-Out Torque	>32 gf·cm at 500 PPS
Insulation Class	Class E
Insulation Resistance	100 MΩ DC 500V
Insulation Strength	100V AC / 1 sec
Operating Temperature	0°C to +55°C
Approx. Weight	47 g, varies by gear ratio

12V Gear Ratio Performance

Gear Ratio	Gearbox Length	Output Step Angle	No-Load Speed @ 700PPS	Holding Torque	Pull-Out Torque
12.5:1	16 mm	1.44°	168 RPM	≥0.5 kg·cm	≥0.3 kg·cm
25:1	16 mm	0.72°	84 RPM	≥1.2 kg·cm	≥0.6 kg·cm
31.25:1	16 mm	0.576°	67 RPM	≥1.5 kg·cm	≥0.75 kg·cm
50:1	17.5 mm	0.36°	42 RPM	≥2.5 kg·cm	≥1.2 kg·cm
62.5:1	17.5 mm	0.288°	33 RPM	≥3.0 kg·cm	≥1.5 kg·cm
78:1	17.5 mm	0.23°	27 RPM	≥3.8 kg·cm	≥1.7 kg·cm
100:1	19 mm	0.18°	21 RPM	≥5.0 kg·cm	≥2.5 kg·cm
125:1	19 mm	0.144°	17 RPM	≤6.0 kg·cm*	≥3.5 kg·cm
156:1	19 mm	0.115°	13 RPM	≤6.0 kg·cm*	≥4.5 kg·cm
195:1	19 mm	0.092°	10 RPM	≤6.0 kg·cm*	≥6.0 kg·cm
250:1	20.5 mm	0.072°	8 RPM	≤6.0 kg·cm*	≤6.0 kg·cm*
312.5:1	20.5 mm	0.0576°	6 RPM	≤6.0 kg·cm*	≤6.0 kg·cm*
390:1	20.5 mm	0.0462°	5 RPM	≤6.0 kg·cm*	≤6.0 kg·cm*
488:1	20.5 mm	0.037°	4 RPM	≤6.0 kg·cm*	≤6.0 kg·cm*

* Important: Maximum instantaneous gearbox load must not exceed 6.0 kg·cm.

Wiring

Wire Color	Phase
Red	A
Yellow	A̅
Black	B̅
Blue	B

Applications

Suitable for miniature robots, positioning mechanisms, smart devices, automated instruments, small actuators, camera mechanisms, electric curtains, educational robotics, and other compact motion-control systems.